Comcast, the owner of NBC, has beaten Rupert Murdoch's 21st Century Fox in the battle for Sky after offering £30.6bn (€34bn) in a dramatic auction to decide the fate of the pay-television group.

The US cable giant made a bid of £17.28 a share to take control of London-listed Sky, substantially ahead of Fox's £15.67-a-share offer.

Buying Sky will make the Philadelphia-based Comcast, which also owns Universal Pictures, the world's largest pay-TV operator with around 52 million customers.

Chairman and chief executive Brian Roberts has had his eye on Sky as a way to help counter declines in subscribers for traditional cable TV in its core US market as viewers switch to video-on-demand services such as Netflix.

"This is a great day for Comcast," he said. "It allows us to quickly and efficiently increase our customer base and expand internationally."

Comcast's knockout offer thwarted Mr Murdoch's long-held ambition to win full control of Sky, and is a setback for Disney, which would have likely been its ultimate owner.

Disney has agreed a separate $71bn deal to buy most of Fox's film and TV assets, including its existing 39pc stake in Sky, and would have taken full ownership after a successful Fox takeover.

Comcast believed it needed to deliver a knockout blow given that Fox's existing stake in Sky gave it a chance of victory if it was a close second to Comcast, two sources said.

Its final offer was more than double what Sky's share price was before Fox made its takeover approach in 2016. "It is a clear sign that legacy media companies are desperate for scale," said Richard Greenfield, an analyst at BTIG.